Telegraph system



July 25, 1939. R LM R 2,167,509

TELEGRAPH SYSTEM Filed Feb. 12, 1937 4 Sheet-Sheet 2 Hy? c July 25, 1939. R, HELMERT 2,167,509

TELEGRAPH SYSTEM Filed Feb. 12, 1957 4 Sheets-Sheet 4 112172177011 fioberff/e/mer/ Patented July 25, 1939 UNITED STATES PATENT OFFICE TELEGRAPH SYSTEM Application February 12, 1937, Serial No. 125,445 In Germany February 14, 1936 5 Claims.

The invention relates to telegraph systems wherein the connections are established over selectors which are set by means of current impulses of a nature similar to the telegraph signals. Due to such similarity the selectors may happen to be set by telegraph signals, whereby undesired connections would be established. This risk is considerably increased if from any cause the connection becomes released in part during a transmission of telegraph signals, because in such event the telegraph signals then given will build up a connection different from the former so that the remainder of the message will be transmitted to a subscriber not intended to receive it.

The invention provides switching means which on a partial release of a connection cause the release of all the other parts thereof and which prevent a re-seizure of selectors by the stations still in calling condition.

If the stations are equipped with telegraph sets which are automatically stopped by a characteristic signal transmitted from the automatic exchange whenever a connection is broken, this stopping too is effected by said switching means. In this way the subscriber is advised by his telegraph set stopping that the connection has been released and that therefore his apparatus has to be re-set.

A premature release of a connection of this kind may occur from various causes. For instance, a final selector may happen to release on account of a blown fuse. Then the first group selector must be prevented from engaging another final selector, that is to say, must likewise be released. Therefore the switching means effecting the release must be allotted to the individual selector stages. If a connection extends over long distance lines and a plurality of automatic exchanges, a partial release may be caused by a transient disturbance occurring in these lines. If, for instance, in the case of a four- Wire circuit such a disturbance occurs in a direction from an exchange A to an exchange B, then exchange B will be released while the selectors in exchange A remain in their operative position. After the disturbance has been removed, the telegraph signals may happen to cause a re-seizure and hence a wrong connection in exchange B. The releasing means must therefore be allotted also to the impulse repeaters. In the said case such means act to transmit a releasing impulse from B to A. As a result the connection is interrupted in exchange A too and the telegraph set of the calling subscriber is disconnected.

The time taken by telegraph signals when carried along a line in which a number of repeaters are included may be so long that it will be necessary to consider the differences of time which the switching operations at the two ends of such line will undergo. Therefore according to the invention the release initiated by the arrival of the releasing signal is forcibly finished by the available switching means and is thus independent of the duration of this signal.

The invention is described hereafter by way of example, reference being had to the accompanying drawings in which- Fig. 1 is a diagrammatic plan of an arrangement with which the invention is applicable. Fig. 2 is a wiring diagram of a teleprinter station indicated in Fig. 1. Fig. 3 is a wiring diagram of preselectors shown in Fig. 1. Fig. 4 is a wiring diagram of group selectors represented in Fig. l,

and Fig. 5 is a wiring diagram of impulse repeaters shown in Fig. 1.

The arrangement illustrated in Fig. 1 comprises two teleprinter stations FSI, FSZ, two preselectors VWI, VW2, two group selectors GWI, GWZ, two group selectors GW3, GW4, two impulse repeaters StrUl, StrUZ, and two final selectors LWI, LWZ.

The teleprinter shown in Fig. 2 comprises a calling key AT, a clearing key ST, a sending contact SK, a receiver magnet EM, a polarized relay P, a relay M, two dial contacts 'nsa, nsi, a condenser C, resistances W2, and a motor M0 for driving the teleprinter. Relay P has a contact 1). Relay M has four contacts ml, m2, m3, m4. Lines a, I) extend into the preselector represented in Fig. 3, as will be seen on the left in Fig. 3.

The preselector shown in Fig. 3 comprises relays E, S, R, N, T, 1-1, a driving magnet D, and an interrupter UD. Relays E, S are polarized. Relays R, N, H are slow acting. Magnet D serves to drive the wipers a, b, c of the preselector VW. Both selectors VWI, VW2 are of this construction. The lines a, b, 0 shown on the right hand side in Fig. 3 extend into the group selector represented in Fig. 4, as will be seen on the left in Fig. 4.

The group selector illustrated in Fig. 4 has relays J, C, Y, P, H, WK, and a driving magnet D that serves to move the wipers a", b, c" of the group selector denoted in a general manner by GW, selectors GWl, GWZ, GW3, GW4 being all of this construction. Relay Y is slow acting. The lines a, b, 0, shown on the right in Fig. 4 extend into the impulse repeater illustrated in Fig. 5, as will be seen here on the left.

The impulse repeater represented in Fig. 5 comprises relays E, S, R, P, C, U, V, and a condenser C0. Relays S and E are polarized. This construction is peculiar to both repeaters StrUl, StrUZ.

The contacts of the relays in Figs. 3, 4, 5 are in a like manner to Fig. 1 designated by the respective small letters and by indices, if necessary.

Let it be supposed that in the arrangement shown in Fig. 1 station FSl has been connected to station FSZ over V'Wl, GWI, StrUi, StrUZ, GW4, LW2. The state of things then is as follows.

In the telegraphic apparatus of the stations PSI and FS2 relay P has closed its contact p and thus energized relay M. Contacts m3, m4 hence are closed so that the motor M0 is running.

In the preselector VW I all the relays shown in Fig. 3 are energized. The armatures of relays E, S are therefore in the opposite position to that represented in Fig. 3 by the contacts e, s. The wipers a, b, c are set to those parts of the lines a, b, c which are connected to the first group selector GWI. Preselector VWZ is in the same condition as VWl except that its wipers are in their position of rest.

In the group selectors GWE, GW l relays C, P, Y, Fig. 4, are energized. Lines a, b are thus corn pletely switched through. They are so in the final selector LW2 too, the wiring diagram of which is not shown because the construction of this selector is immaterial to the idea of the invention.

In repeater StrU i all the relays shown in Fig. 5, except relay P, are energized. The armatures of the relays E, S are in the position opposite to that illustrated in Fig. 5 by the contacts 6. s.

In repeater StrUZ all the relays are energized, except relay C, Fig. 5.

Let it be assumed that relay R of the preselector, Fig. 3, accidentally releases during a transmission of telegraph signals. This relay being slow to release remains energized as long as normal telegraph signals are given and is released only by a short-circu t of a longer duration, namely the short-circuit established by contact e. As soon as relay R when (lo-energized opens its contact T2 the relay T of the preselector and C of the first group selector immediately release. No matter whether relay R is again operated or not the following operations take place on the release of relay T.

Relay S moves its armature into the position represented in Fig. 3 by contact s, and relay N releases slowly, having two windings that counteract each other. The contacts 11!. 722 thus switched reverse the current direction in the lines a, I) connected to the teleprinter. Fig. 1. As a result relay P, Fig. 1. being polarized retracts its armature so as to cut out relay M and thereby to disconnect motor Mo. Contact m2 of relay M acts to interrupt the direct current circuit of the subscribers line, whereby relay R, Fig. 3, is definitely short-circuited, when relay H too is able to release. Only then the preselector is ready to receive a new call, namely a call given by the subscriber depressing the calling key AT. On the de-energization of relay C the group selector is released in a well known manner first by relay P becoming cut out, whereupon the selector is returned to normal. The release of the group selector in turn entails the release of the repeater StrUl since relay C thereof drops its armature, relay S under the action of contact 0! hence retracting its armature into the position illustrated by contact s. In consequence thereof relay E of the repeater StrUZ retracts its armature so as to short-circuit the relay R which therefore is deenergized. Contact r2 thus cuts out relay P and de-energizes line 0, Fig. 5, connected to selector GW4 which hence is likewise released. As soon as the relay P drops its armature the other release operations occur, no matter whether relay R is again actuated or not. First of all relay S of the repeater StrUZ retracts its armature, thus causing relay E of repeater StrUI to short-circuit relay R thereof. As a result relay U is cut out by contact r3 and then relay V out out by contact ul. These two relays release slowly. Only now the repeater can be engaged by a group selector. Equally, relays U, V of repeater StrUZ are cut out on the release of relay P. Selector GWA is released in the same manner as selector GW I. The release of GW4 entails that of selector LW2 which in its turn acts to interrupt line 0 connected to selector VWZ, so as to de-energize relay R thereof, whereby teleprinter FS2 is stopped as described with reference to selector VWI. It will be seen that in this way the entire connection has been released.

Assume now that relay R of the current repeater, Fig. 5, happens to release during a transmission of telegraph signals. In such event contact r! will interrupt line 0 connected to selector GWI. As a result relay C of the impulse repeater and relay P of selector GWI are de-- energized. release of relay C acts to switch relay S so that S retracts its armature into the position illustrated in Fig. 5 by contact 3, whereby repeater StTUZ releases as before described. The de-energization of the relay P of selector GWI causes negative potential to be applied to line b connected to the preselector. Here, relay N is de-energized thereby, thus disconnecting the teleprinter FSI in the manner before set forth. Hereupon relay R of the preselector, Fig. 3, is deenergized so as to release the selector, and the release of relay R entails that of relay C of the first group selector so as to effect also here the desired disconnection.

These two examples show that whenever a connection is interrupted at any point of the system the releasing characteristic will be transferred from that point forward and backward to the subscribers apparatus and stop these.

What is claimed is:

1. In a circuit arrangement for interconnecting in a telegraph system subscribers telegraph apparatus, means including selectors and switching means for establishing a telegraph connection, means including a direct current loop and a calling key therein at each subscribers station for producing current impulses similar to telegraph signals for setting said selectors, means for operating said switching means in setting up said connection, means for disabling said switching means in case of a premature partial release of the connection, and means including the last mentioned means to postpone the establishment of a new connection until all selectors and switching means in the first mentioned connec tion have been released and until the loop at the calling subscribers station has been closed by operating the calling key.

2. Circuit arrangement according to claim 1 in which means are provided for stopping subscribers telegraph apparatus, and means controlled by said switching means for actuating the means for stopping.

3. Circuit arrangement according to claim 1 5. In a circuit arrangement according to claim 1, a release signal actuated upon the partial release of the connection, and means separate and independent from said release signal and operative subsequent to the partial release for completely releasing the connection.

ROBERT HELMERT. 

